解析 A核心短语/词汇:help sb./ sth. (to) do sth. 帮助某人/某物做某事句子译文:氧气是唯一的助燃气体吗? 本题考查定语从句。___helps fire burn 用来修饰之前的名词gas, 该从句的引导词在定语从句中做主语,不能省略,先行词有only 修饰时不能用which; what 不能引导定语从句,故选项A符合题意。反馈...
An important part of chemistry is being able to understand the various useful features of the periodic table of the chemical elements. These features include the atomic number, row position and column position of each element. Each row is a period and each column is a group. All groups are ...
What does the atomic number of an element indicate? What is the symbol of the element in Group 4A (14) and Period 2? a. Be b. Mg c. Ca d. C e. Si What's the symbol for Oxygen on the periodic table? The symbol Ag stands for which element? a. Gallium b. Magnesium c. Gold...
The periodic table is the most important chemistry reference there is. It arranges all the known elements in an informative array. Elements are arranged left to right and top to bottom in order of increasing atomic number. This order generally coincides with increasing atomic mass The different ...
What is the maximum oxygen percentage allowed in a tank? A. 12% B. 6% C. 8% D. 10% 如何将EXCEL生成题库手机刷题 如何制作自己的在线小题库 > 手机使用 分享 反馈 收藏 举报 参考答案: C 复制 纠错 举一反三 全力构建“14355”财务发展目标框架,大力实施财务金融一体化、()、集约化管控...
The ocean covers more than 70% of the Earth’s surface. It produces at least half of the planet’s oxygen and absorbs around 30% of the carbon dioxide produced by humans. The sea is home to most of our biodiversity and 3 billion peop...
Oxygen is not dangerous. Byanon229958— On Nov 16, 2011 Oxygen concentrators are quite amazing. They help so many people with respiratory problems by concentrating air with oxygen and delivering it to them. The best part of that is that now those who couldn't go out and do things because...
解析:考查定语从句.先行词 gas,helps fire burn是定语从句,关系词在定语从句中做主语,指物,又因为先行词被the only修饰,故用that.故选:A. 氧气是能帮助火燃烧的唯一气体. 结果一 题目 Is oxygen the only gas helps fire burn? A.thatB./C.whichD.it 答案 A此句为定语从句,当先行词gas前有the on...
Themodern periodic tableis very similar to Mendeleev's table, but elements today are ordered by increasingatomic number, which reflects the number ofprotonsin an atom. There aren't any "undiscovered" elements, althoughnew elementscan be created that have even higher numbers of protons. ...
One of the most common GHGs, CO2, is found in the Earth’s atmosphere and, along with nitrogen, oxygen, methane, and other gases, is part of the planet’s air. CO2 helps trap heat on Earth, like a greenhouse traps heat to grow tomatoes in cold climates. But too much of it can ...